Liquid–Liquid Extraction of Butanol from Heptane + Butanol Mixture by Ionic Liquids

Selection of a suitable solvent is the key for the extraction process. In this work, four ionic liquids were selected as solvent for extracting butanol, the ternary liquid–liquid equilibria (LLE) data for systems of heptane + butanol + {[HMIM][BF4] (1-hexyl-3-methylimidazolium tetrafluoroborate), [OMIM][BF4] (1-octyl-3-methylimidazolium tetrafluoroborate), [HMIM][OTf] (1-hexyl-3-methylimidazolium trifluoromethansulfonate), and [HMIM][NTf2] (1-hexyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)imide)} were measured at 298.15 K and atmospheric pressure. The extraction capacity of four ILs in the separation of butanol from heptane + butanol mixture was estimated by the selectivity (S) and solute distribution ratio (β), and the influence of the structure and anion of IL on the extraction efficiency was investigated. The experimental LLE data were correlated by using NRTL and UNIQUAC models.